Conventionally, an arrangement in which an oxygen concentration of a monocrystal is controlled is known (see, e.g., patent documents 1 and 2).
According to the patent document 1, when a silicon rod is manufactured using a crystal pulling-up apparatus, as a length of the silicon rod increases, a gas pressure of atmosphere over the silicon melt material is increased to limit evaporation of a silicon oxide material, thereby compensating decrease of oxygen contained in the melt material.
According to the patent document 2, when a silicon monocrystal is manufactured using a silicon monocrystal pulling-up apparatus, a flow rate of inactive gas flowing between a gas guide and a silicon melt is adjusted so that the flow rate is gradually accelerated from the start of the pulling-up toward the end of the pulling-up.
Patent Document: JP-A-10-182289
Patent Document: JP-A-5-70279